Strategies for enhancing security of energy supply and mitigation of energy-related GHG emissions, include, inter alia, the need for: increased energy efficiency (i. e. decreasing energy use per unit of product, process or service); increased use of clean fossil energy (i. e. use of fossil fuels coupled with CO2 sequestration and storage); and increased use of carbon neutral renewable energy, mainly biofuels [23, 196]. Conditions for technically and economically viable biofuel resources are that, they should be [100, 195]: cost-competitive against petroleum-based fuels, require low to no additional land use, enable air quality improvements (e. g. CO2 sequestration), and require minimal water usage. Biofuels are technically carbon neutral, i. e. the release of CO2 during conversion is equivalent to what is captured during growth of the parent material via the photosynthesis process [ 1] . However, they may not always be carbon neutral where energy from fossil fuels are used in the cultivation, harvesting, manufacture of fertiliser and herbicides, processing, and direct conver­sion to energy or specific energy carriers as depicted in the illustration in Fig.1 for biomass from willow short rotation coppice.

The deployment of first — and second-generation biofuels has generated a lot of controversy, mainly due to the negative impact on global food markets [144] and

energy-intensive processes for conversion to fuels [226], respectively. Any effort towards increased production of biofuel-directed biomass must therefore consider the overall sustainability. Microalgae-derived biofuels are devoid of the major drawbacks associated with first — and second-generation biofuels. Their judicious exploitation could therefore make a significant contribution to meeting the primary energy demand, while simultaneously providing environmental benefits [218]